Boulder scientists leading solar energy forecast project

NCAR directing project under $4.1 million grant from DOE

By Charlie Brennan Camera Staff Writer

Posted:
02/22/2013 06:37:13 PM MST

Solar energy power plants around the country are expected to benefit from a new three-year project spearheaded by the National Center for Atmospheric Research that strives for better forecasting of incoming energy from the sun.

The work is to be mainly funded through a $4.1 million U.S. Department of Energy grant, and will be spearheaded by Sue Ellen Haupt, director of NCAR's Weather Systems and Assessment Program in Boulder.

This does not mark NCAR's first foray into the field of renewable energy. Previously, NCAR designed a wind energy forecasting system for Xcel Energy that saved Xcel customers about $6 million in a single year.

"It's critical for utility managers to know how much sunlight will be reaching solar energy plants in order to have confidence that they can supply sufficient power when their customers need it," Haupt said. "These detailed cloud and irradiance forecasts are a vital step in using more energy from the sun."

The sun's energy can be compromised by everything from cloud cover to aerosols or other pollutants in the atmosphere to the contrails of airplanes that can linger and evolve into cirrus clouds.

The goal of the program is to be able to help utilities tap solar energy more effectively, by giving detailed cloud-cover predictions so that utilities can program their generation of other power sources accordingly. Large amounts of electricity can't be stored in a cost-effective manner, so power originating from a solar panel or any other source must be promptly consumed.

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"For instance," Haupt said, "if there is a cold front coming through and we can predict the timing, the type of cloud and the extent to which it will block the sun, that is helpful to the utility in planning what big base-load units they will have to be running.

"And then, on the very short term, if we can tell them next hour how many cumulous clouds will be going over, that helps them integrate that into their grid and provide a reliable lower-cost energy source."

Forecasts will be provided at 15-minute intervals, out to 36 hours. The forecasts are expected to be updated at least hourly.

Making up for loss

For solar energy power plants, Haupt said, the loss of solar energy due to clouds and other factors "is not a problem if they know when it's going to occur and when it isn't. They have to be able to know when to run their base-load or medium-load units to make up for the loss of renewables."

Solar energy is influenced not only by the presence of clouds, but also by the type of clouds that form. The elevation and the thickness of clouds have varying effects on the amount of sunlight that reaches the earth's surface.

To create a system that will generate sufficiently detailed forecasts, NCAR and a large cast of partners will deploy an array of technology. The project will utilize specialized computer models, and mathematical and artificial intelligence techniques. Instruments used will include lidars, devices that employ laser-based technology to record measurements in the atmosphere.

A key part of the project involves the use of three total-sky imagers in locations ranging from the northeast to California and Florida, as well as Colorado and New Mexico, to observe the total sky, triangulating the height and depth of clouds and tracing their movement across the sky.

Once the system has been tested, it is expected that it will have broad applications, far beyond the primary focus of serving utilities.

"One of the examples is, it can be used to predict pavement temperatures for surface transportation, including racing teams," Haupt said. "Some of the other things we're doing is predicting, based on cloud clover, how much melting there is going to be on in the roads in the winter, here in Colorado.

"All of these things fit together beautifully and when you improve one piece of the model, it's good for the rest."

Partnering up

NCAR is hardly alone in the solar energy forecasting venture. It is initiating the project with a long list of partners in both the public and private sector.

They include, but are not limited to, the National Renewable Energy Laboratory, the National Oceanic and Atmospheric Administration's Earth System Research Laboratory and other NOAA facilities, Colorado State University, the University of Washington, Xcel Energy, Long Island power and Light, Hawaiian Electric, Southern California Edison, and more.

Computing time will be provided by the New York State Department of Economic Development's Division of Science, Technology and Innovation.

Many participants in the project will be coming to Boulder the second week of March to map out the next steps in the program.

"There's good scientists all over the country, and we're involving many of them," Haupt said. "It's a great opportunity to leverage what a lot of people have done, and leverage the synergy that you can create with a team like this."

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